// For flags

CVE-2026-31809

SiYuan has a SVG Sanitizer Bypass via Whitespace in `javascript:` URI — Unauthenticated XSS

Severity Score

6.4
*CVSS v4

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track*
*SSVC
Descriptions

SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (	), newline (
), or carriage return (
) characters inside the javascript: string bypasses this prefix check. Browsers strip these characters per the WHATWG URL specification before parsing the URL scheme, so the JavaScript still executes. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint, creating a reflected XSS. This is a second bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in 3.5.10.

SiYuan es un sistema de gestión de conocimiento personal. Antes de la versión 3.5.10, el saneador de SVG de SiYuan (SanitizeSVG) verifica los atributos href en busca del prefijo javascript: utilizando strings.HasPrefix(). Sin embargo, la inserción de caracteres de tabulación ASCII ( ), nueva línea (
) o retorno de carro ( ) dentro de la cadena javascript: elude esta verificación de prefijo. Los navegadores eliminan estos caracteres según la especificación de URL de WHATWG antes de analizar el esquema de URL, por lo que el JavaScript aún se ejecuta. Esto permite a un atacante inyectar JavaScript ejecutable en el endpoint no autenticado /API/icon/getDynamicIcon, creando un XSS reflejado. Este es un segundo bypass de la corrección para CVE-2026-29183 (corregido en la v3.5.9). Esta vulnerabilidad se corrige en la versión 3.5.10.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
System
Vulnerable | Subsequent
Confidentiality
None
High
Integrity
None
High
Availability
None
None
* Common Vulnerability Scoring System
SSVC
  • Decision:Track*
Exploitation
Poc
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2026-03-09 CVE Reserved
  • 2026-03-10 CVE Published
  • 2026-03-11 CVE Updated
  • 2026-04-21 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Siyuan-note
Search vendor "Siyuan-note"
 Siyuan
Search vendor "Siyuan-note" for product "Siyuan"
 < 3.5.10
Search vendor "Siyuan-note" for product "Siyuan" and version " < 3.5.10"
en
Affected